1. Field of the Invention
The present invention relates to motor operators for circuit breakers. More specifically, the invention relates to an improved structure and method of assembly for a motor operator, providing a bearing insert at each end of the screw shaft, with the bearing adapted for easy insertion into opposing walls of the motor operator""s housing.
2. Description of the Related Art
Circuit breakers are frequently actuated remotely, by securing a motor operator over the face of the circuit breaker, so that the motor operator can actuate the circuit breaker. A typical motor operator includes an electric motor, operatively connected through a system of gears to a threaded rod. A sliding actuator is threadedly connected to the threaded rod, so that rotation of the threaded rod causes the sliding actuator to reciprocate back and forth. The sliding actuator fits over the circuit breaker""s operating handle, so that movement of the actuator moves the operating handle. A kill/toggle switch at each end of the sliding actuator""s range of travel shuts off the current, and reverses the direction of current that will be supplied to the motor, upon being depressed by the sliding actuator. A printed circuit board will typically contain the motor operator""s control circuitry. When the user transmits a signal to close the circuit breaker, the control circuitry will supply current to the motor, thereby rotating the threaded shaft to slide the sliding actuator from one end of its range of travel to the other, thereby moving the circuit breaker""s operating handle, and closing the circuit breaker. Upon reaching the end of its range of travel wherein the circuit breaker is closed, the sliding actuator hits the toggle switch at that location, thereby shutting off current to the motor, and reversing the direction of current to the motor. When the user transmits a signal to open the circuit breaker, the control circuit will again supply current to the motor, thereby moving the sliding actuator to the opposite end of its range of travel, moving the circuit breaker""s operating handle to its open position. As before, when the sliding actuator reaches the position wherein the circuit breaker is open, it strikes a kill/toggle switch, shutting off current to the motor, and reversing the direction of current flow to the motor.
The screw shaft of presently available motor operators is secured between opposing walls of the housing, so that assembly of the motor operator requires first installing various washers, retaining rings, bearings, a gear, and a sliding actuator on the screw shaft, bending the housing, inserting the screw shaft between the appropriate walls, and then allowing the housing to deflect back to its original position. In addition to making assembly of the motor operator unnecessarily difficult, the present design also precludes automated assembly of the motor operator.
Accordingly, a motor operator having an improved structure permitting simplified, and possibly automated, assembly is desired. Additionally, an improved method of assembling a motor operator is desired.
The present invention provides a bearing insert for the screw shaft of a motor operator, thereby permitting the screw shaft to be installed within the housing without the need to bend the opposing housing walls away from each other.
A preferred embodiment of the bearing insert is generally rectangular, and some embodiments may have a radiused or tapered bottom end. The bottom end of the bearing insert includes an aperture dimensioned and configured to receive one end of a screw shaft for a motor operator. The sides and bottom of the bearing insert include a plurality of flanges, dimensioned and configured to fit along both sides of the wall of a motor operators housing. In some preferred embodiments, at least one of these flanges may be extended, and may define an aperture, such as a threaded aperture, for receiving a screw or bolt.
To assemble a motor operator incorporating the present invention, a gear, sliding acuator, and other components typically installed on the threaded rod are first installed on this rod. Next, a bearing insert of the present invention is installed on each end of the screw shaft. The bearing inserts are then placed into channels dimensioned and configured to receive them, defined within opposing walls of the motor operators housing, with the flanges of each bearing insert fitting on each side of its corresponding wall. Lastly, bolts or screws may be passed through apertures within the housing, into the screw holes defined within the bearing insert.
Placing the screw shaft between a pair of bearing inserts of the present invention, and then installing the bearing inserts into appropriately configured channels within opposing walls of the motor operators housing, eliminates the need to bend the opposing walls of the motor operators housing away from each other in order to fit the ends of the screw shaft with an aperture as defined directly within these walls. Additionally, eliminating the need to bend the walls of the motor operators housing raises the possibility of using automated assembly methods, thereby reducing the cost of the motor operator.